In recent years, communication technologies utilizing optical fibers have been coming into wide use. In order to realize a long-haul signal transmission using an optical fiber, it is necessary to perform optical axis alignment between optical fiber parts and then couple the optical fiber parts by, e.g., welding, so that the coupling loss between the optical fiber parts is reduced.
Optical axis alignment of this kind between optical fiber parts is performed as follows. For example, in the case of optical axis alignment between two optical fiber parts, each of the fiber parts is fixed to the distal end of a stage, which is driven by a motor and has a multi-degree of freedom, so that the optical axis alignment between the two optical fiber parts is performed while moving the stages. More specifically, the two optical fiber parts are separated from each other with a predetermined small gap therebetween, and one or both of the stages are moved, while the light quantity passing through the two optical fiber parts is measured. The operation is performed to find a position where the light quantity passing through the two optical fiber parts is at the maximum. At this position, the two optical fiber parts are brought into face contact with each other and welded or so, so that they are fixed to each other.
In the optical axis alignment method described above, the optical axis alignment is performed while the optical fiber parts are separated from each other, and then the two optical fiber parts are brought into face contact with each other. Consequently, the optical fiber parts can cause a minute positional shift when they are moved, which makes it difficult to minimize the coupling loss between the optical fiber parts. For this reason, it may be preferable to perform optical axis alignment between optical fiber parts while the optical fiber parts are kept in face contact with each other. In conventional optical axis alignment apparatuses, however, when two optical fiber parts, which are kept in face contact with each other to have surface friction, are relatively moved with a predetermined force, a stick-slip phenomenon occurs at the contact surfaces and makes it difficult to delicately move the optical fiber parts in a stable state.
Furthermore, in conventional optical axis alignment apparatuses, where the contact surfaces of optical fiber parts tilt, the angle between the optical fiber parts have to be adjusted to make sure that the contact surfaces are brought into face contact with each other. In this case, it is necessary for a used tilting mechanism to make a delicate adjustment of the angels of the contact surfaces, and thus the tilting mechanism needs to have a complicated structure, thereby increasing the size of the optical axis alignment apparatus. In addition, the price of the optical axis alignment apparatus is also increased.